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A293866
For n > 2: when computing A229037(n), there are up to floor((n-1)/2) forbidden values (i.e. values that would lead to an arithmetic progression); a(n) = greatest forbidden value when computing A229037(n).
3
1, 3, 3, 1, 3, 3, 6, 6, 7, 7, 7, 7, 7, 7, 7, 6, 6, 7, 7, 7, 7, 7, 11, 11, 12, 13, 14, 12, 13, 14, 14, 15, 16, 14, 15, 16, 16, 17, 17, 16, 17, 17, 14, 15, 16, 16, 17, 17, 16, 17, 17, 12, 13, 14, 13, 13, 14, 14, 15, 16, 16, 16, 16, 18, 17, 24, 17, 21, 21, 18, 21
OFFSET
3,2
COMMENTS
The scatterplot of this sequence has interesting features, such as rectangular clusters of points.
For any n > 2, A229037(n) <= a(n) + 1, with equality for n=3, 6, 8, 24 (and possibly no other values).
FORMULA
a(n) = max_{j=1..floor((n-1)/2)} (2*A229037(n-j) - A229037(n-2*j)).
EXAMPLE
For n=7: A229037(7) must be distinct from:
- 2*A229037(7-1) - A229037(7-2) = 2*2 - 1 = 3,
- 2*A229037(7-2) - A229037(7-4) = 2*1 - 2 = 2,
- 2*A229037(7-3) - A229037(7-6) = 2*1 - 1 = 1.
Hence a(7) = 3.
PROG
(C++) See Links section.
CROSSREFS
Cf. A229037.
Sequence in context: A125562 A337910 A092040 * A161200 A214747 A110766
KEYWORD
nonn,look
AUTHOR
Rémy Sigrist, Oct 18 2017
STATUS
approved